Artesia Tower, Mumbai, India – Vertical Post Tensioning of Reinforced Concrete Core Wall

Amitabh Kumar
Sr. Vice President
Puranik Builders Pvt. Ltd, Mumbai

Artesia, a 240 M high, residential tall tower is under construction in downtown Mumbai. Residential flats facing away from the Arabian Sea beyond 106.5 M have been omitted and stacked on the sea-facing side with spectacular view. Concomitantly, floor plates in the overall structure were reduced by 40 percent beyond 106.5 M. This design approach needs deliberate asymmetrical massing of the tower, which has resulted in predominant tensile stresses in 35 percent of the total core wall length measured on the plan. The reinforced concrete core wall has been vertically post-tensioned up to a height of 150 M, using 50 mm diameter high-tensile threaded steel bars (1030 MPa) to neutralize tensile stresses—an innovative approach. To verify the effectiveness of the design, stresses and deflection of the core wall have been computed and compared with alternative conventional designs without post-tension. Post-tension forces, coupled with wind load induced forces, necessitate M 80 / M 70 grade concrete in the core wall. Post-tensioned bars, within HDPE corrugated ducts, have been stressed at nine different levels across the height of the building, from the raft at the bottom to 150 M height and are grouted throughout. The post-tension of the core wall increases construction time, which is compensated using Core Preceding Construction Method for faster slab-cycle. All stressing levels have been carefully incorporated with the climbing sequence of the core wall’s shuttering. Thickness of the core wall, stressing levels, and outrigger connections was carefully designed and planned. Post-tension enhances the core wall’s performance and durability over the life cycle of the tower by neutralizing tensile stresses and controlling inelastic creep deflection caused by asymmetrical massing.